The present invention concerns an optical waveguide device fabrication method comprising providing at least one optical waveguide or optical waveguide core; and depositing at least one silicon dioxide layer or material onto the at least one optical waveguide or optical waveguide core to form a cladding or passivation layer of the optical waveguide device. The at least one silicon dioxide layer or material is deposited by plasma-enhanced chemical vapor deposition using precursors comprising or consisting of silicon tetrachloride and at least one oxidizer, the plasma being an inductively coupled plasma.